Photoelectric tube



Jan. 16, 1940. H. M. BIELE 2,187,434

' PHOTOELECTRIC TUBE Original Filed Feb. 10, 1938 FIG. I

INVENTOR HARRY M. BIELE sa L I ATTORNEY Patented Jan. 16, 1940 UNITEDSTATES PATENT OFFICE PHOTOELECTRIG TUBE Harry M. Biele, Hollis, N. Y.,assignor to Associated Press, New York, N. Y., a. corporation of NewYork 1 Claim.

This application is a division of Serial Number 189,773, filed Feb. 10,1938.

This invention relates to a photoelectric tube. An object of theinvention is to provide a photo- 5 electric tube of high efliciency andsimple construction particularly adapted for use with picture scanningsystems.

Other objects will appear in the following de- 10 ing drawing of whichFigure 1 is a schematic view of a scanning device, partly in section; V

Figure 2 is a horizontal section of the photoelectric tube according tothe present invention.

Referring now to Figure 1 of the drawing: Reference character Iindicates a scanning cylinder about which the picture to be scanned iswrapped. Light from a light source 2 shines through a condenser lens 3,through optical system 4 which projects the light onto the surface ofthe cylinder at the point 5. A diliused light varying in intensityaccording to the shading of the elemental tone areas of the picture isreflected onto the cathode of a photoelectric tube of novelconstruction, now about to be described.

Heretofore, it has been customary to use various arrangements of mirrorsfor collecting the difiused light from the picture being scanned, but ithas been found that such systems are needlessly inefiicient in that aconsiderable amount of light is absorbed by the reflecting mirrors.

The use of mirrors is eliminated by the photoelectrictube of the presentinvention, the novel scription given with the aid of the acc0mpany-.

construction of which permits the objective of the optical system to beplaced close to the picture thus making it possible to use a highlyefficient short focus lens assembly. The tube consists of a glassenvelope 6 of tubular shape through which an optical system extends.Inside the envelope 6 is a tubular cathode l and a concentricallydisposed anode 8 which is preferably ring shaped.

Any suitable mounting or supporting means may be used for the partscontained in the glass envelope. Likewise, any suitable means may beused for providing external connections for the anode and cathode. Byreferring to the drawing it will be seen that the difiused light in thepresent embodiment, reflected at from 15 to 45 degrees will falldirectly on the cathode of the photoelectric tube which may be placedvery close to the pencil of light impinging. on the cylinder at 5,resulting in a very simple and eificient scanning system with noappreciable light loss.

What is claimed is:

A photoelectric tube including a tubular doublewalled vessel forming anunobstructed longitudinal passage therethrough and having a transparentwindow, an open ended tubular cathode having a continuousphoto-sensitized surface the active area of which is a portion thereofto be exposed to light when in use, said cathode being mounted in saidvessel substantially concentrically with said passage, and an anode insaid vessel surrounding said passage adjacent the end of said activearea and lying within said cathode.

HARRY M. BIELE.

